What product is expected from the reactino of fumaric acid (trans-2-butenedioic acid) with 1,3-butadiene?

Answer 1

This is a Diels-Alder reaction.

You will get 4-cyclohexene-1,2 dicarboxylic acid

You will need to work out the stereochemistry, but for the general structure see

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Answer 2

cyclohex-4-ene-trans-1,2-dicarboxylic acid